I am very rarely in a position where I have to leave my EDC in my truck. What I have done it put a cable lock around both the driver and passenger seat posts with the key in the lock. If I have to leave my gun, or if a passenger needs to, I slip the cable lock through the barrel, close the lock and take the key. The gun stays hidden under the seat but locked to the post in the even of a break in. It's not perfect, but a simple solution for something I might use once every two or three years.

“While the people are virtuous they cannot be subdued; but when once they lose their virtue then will be ready to surrender their liberties to the first external or internal invader.” ― Samuel Adams

karder wrote:What I have done it put a cable lock around both the driver and passenger seat posts with the key in the lock. If I have to leave my gun, or if a passenger needs to, I slip the cable lock through the barrel, close the lock and take the key. The gun stays hidden under the seat but locked to the post in the even of a break in.

I like this answer. I also try to park somewhere conspicuous, like near the entrance, under a lamp, etc. where people will be less likely to want to target my vehicle.